The invention generally relates to medical devices such as baskets for retrieving material from within a body. More particularly, the invention relates to releasable baskets for retrieval of stones such as urinary tract stones, gall stones, and other biological materials.
Medical retrieval baskets generally are used to retrieve biological and foreign material from the body including stones. Such baskets may be used through an endoscope or a laparoscope, for example.
In existing medical retrieval baskets, the contour of the baskets generally are round, oval, or pear-shaped, and the baskets are formed by a plurality of legs. Stones or other biological materials are captured in the basket by moving the basket around the material to be retrieved and maneuvering the material into the basket through the space between the basket legs.
After the material is captured in a known basket, it is generally difficult to release the material from the basket if release of the captured material is required or indicated. The technical difficulty in releasing material such as a captured stone is a characteristic of known medical retrieval baskets in general In some patients with long-standing clinical problems with urinary tract stones, a cicatrix may form in the tract as a result of trauma to its lining. The stenosis created by the cicatrix may not be so narrow so as to interfere with insertion of a retrieval basket while the basket is in a closed position. However, after the basket is expanded to capture the stone that is lodged beyond the stenotic area of the tract, the diameter of the basket containing the captured stone may exceed the diameter of the stenotic region of the urinary tract. Under these circumstances, release of the stone from the basket is a prerequisite for withdrawal of the device from the urinary tract. If the stone can not be released, more invasive, surgical approaches are required to disengage the stone from the basket.
Also, known baskets must be eased beyond the stone or to one side of the stone to permit entry of the stone into the basket. This maneuver can be technically very difficult. The narrow diameter of the tract lumen, compounded by the formation of stretch resistant scar tissue in the tract at the situs of the stone can severely limit the space around which the basket can maneuver. Moreover, the tract lining may become so attenuated at the site of the stone that advancing the basket to one side of the stone may risk rupture of the tract.
When expanded, existing baskets also generally lack dilatative strength. That is, known baskets generally are not resistive to forces countering basket expansion. The lack of dilatative strength in existing baskets is usually the result of flexible basket legs which are helpful in facilitating the entry of a stone into the basket but which decrease dilatative strength. Consequently, existing baskets generally are not effective at dilating the tract.
The invention relates to medical retrieval baskets with enhanced basket strength and with features that permit both end-encapsulation and, when indicated, release of biological material. The basic medical retrieval basket design as contemplated by the invention is an end-encapsulation basket formed by a plurality of loops supported by members disposed between the loops.
Baskets according to the invention have several advantages over other known baskets. One advantage is the feature that allows stone capture by end-encapsulation. The basket is formed by a plurality of loops, the loops are joined at the basket base, and have an unattached end at the distal portion of the basket. The basket loops are moveable between a closed position and an open position. In the open position, the ends of the loops are parted. When the basket is maneuvered into a body tract to capture material such as a stone, the basket is in a withdrawn position collapsed within the sheath. As the end of the sheath approaches the stone, the basket is extended from the sheath. The basket loops are moved between a closed position and an open position where the unattached ends of the loops are parted. With the unattached ends of the loops parted, the basket is advanced directly over the stone at the front end of the basket. The stone is end-encapsulated when the stone enters the basket through the space created by the parted unattached ends of the basket loops. The end-encapsulation basket design obviates the need for passing the basket to one side of, or beyond, the stone in order to capture the stone. The basket can xe2x80x9cpluckxe2x80x9d stones from embedded regions such as the calyx of a kidney. Once the stone is captured in the basket, the unattached ends of the basket loops are juxtaposed by returning the basket loops to the closed position. The stone is thereby captured and the medical retrieval device with the captured stone is removed from the body tract.
Another advantage of baskets according to the invention is that they dilate the tract. Dilation of the tract around the stone permits greater basket maneuverability thereby facilitating stone capture. Also, dilation of the tract, as the captured stone and basket are withdrawn from the tract, diminishes the potential damage that may be caused to the tract lining by ragged stone edges.
Still another advantage of a basket of the invention is the ability to release captured material. After material (e.g., a stone) is captured in the basket, the unattached ends of the basket loops may be parted by moving the basket loops from the closed position to the open position. The stone then may be released from the basket between the parted unattached ends of the basket loops.
In one aspect, the invention relates to a medical device for retrieving material from a body. The device comprises a proximal handle, a sheath, and a basket. The sheath extends distally from the handle and has a lumen extending therethrough from a distal end of the sheath to a proximal end of the sheath. The basket is moveable relative to the sheath between a withdrawn position in which the basket is collapsed within the lumen of the sheath and an extended position in which the basket extends from the distal end of the sheath and is disposed outside of the lumen. The basket has a base and a distal portion when in the extended position, and the basket comprises at least two loops which are joined at the base and which are unattached to each other at the distal portion of the basket. The loops are moveable when the basket is in the extended position between an open position and a closed position with the loops being closer together at the distal portion when in the closed position than when in the open position. This device can be used, according to another aspect of the invention, to retrieve material (biological or foreign) from a body by inserting the device, extending the basket from the sheath and moving the basket loops from a closed position to an open position, capturing the biological material within the basket, retracting the loops into the sheath wherein the unattached ends of the loops are juxtaposed thereby moving the basket to a substantially closed position, and withdrawing the basket from the body to remove the material from the body.
In one embodiment of the invention, the proximal ends of the basket loops forming the basket base are operably attached to an elongate member (e.g., a cable or wire), and the elongate member is moveable within the sheath along its length. In the withdrawn basket position, the basket is collapsed within the sheath and the unattached ends of the basket loops are together and touching. When the elongate member is advanced, the basket is extended out of the sheath moving the basket to the extended position and the unattached distal ends of the basket loops part. The basket loops thereby assume an open basket loop position by the inherent elasticity of the basket loops as movement of the elongate member causes the loops (i.e., the basket) to extend outside of the sheath. Reversing the movement of the elongate member by withdrawing it within the sheath, moves the basket loops back within the sheath and collapses them.
In another embodiment of the invention, when the basket is in the extended position, the inherent elasticity of the basket loops maintains the basket in the closed position, and wires are operably attached to an intermediate portion of the basket loops at one of the ends and to a second elongate member within the sheath by the other end. The unattached ends of the basket loops are parted when traction is applied to the second elongate member, tensing the wires, and pulling the unattached ends of the basket loops apart. The basket loops are thereby moved from a closed position to an open position.
Other embodiments of devices, according to the invention include the following features. For example, a channel can be disposed through the sheath of the retrieval device, and a push rod can be axially disposed within the channel through the basket base and into the lumen of the basket. The push rod can be used to push material, such as a stone, out of the basket through the parted unattached ends of the basket loops. Furthermore or alternatively, a ram-rod or other lithotriptic device can be disposed in the channel for fragmenting the material captured and stabilized within the basket.
The basket loops can be supported by support members disposed between the loops of the basket. The support members improve the basket strength. Improved basket strength enhances stone gripping and improves dilatative force that can be exerted by the retrieval device of the invention.
Material such as mesh or woven material may be disposed in the loops of the basket. The basket loops with the disposed material within the loops may form opposing concave or cuplike structures for holding the captured material.
At least a portion of at least the inner surfaces of the basket loops can be modified to improve stone gripping. For example, all or a portion of the inner surfaces of the loops can be coated with an anti-slip substance such as a rubberized material or roughened in some manner (e.g., by serrations, abrasions, etching, etc.) to increase friction between the inner surfaces of the basket loops and the captured material.
It is possible with baskets according to the invention to remove polyps such as gastrointestinal polyps. In such embodiments, the basket loops are energized (e.g., with electrical energy such as RF energy) to excise a polyp. Also or alternatively, the basket loops may have a cutting surface. Polypectomy may be performed and the polyps preserved in the basket for subsequent pathological examination.
The invention also contemplates methods related to the baskets such as methods for constructing the basket loops from a single piece of material a flat, substantially oval, symmetrical template. The template has oppositely disposed ends and is removed from the single piece of material. As part of the manufacturing process, the material is subsequently bent and folded to form the basket structure. The bends and folds provide elasticity to the opposed loops. The elasticity introduced by folding and bending the basket materials is taken advantage of to open and close the basket loops.
In another aspect of the invention, a method for manufacturing a medical retrieval basket comprises removing a flat, substantially oval template from a single piece of construction material. The template is symmetrical and has a first end and a second end, with the first and second ends being oppositely disposed. The template is then folded such that the first and second ends of the template are brought together, and the joined ends are then secured together.